Immediateforce-feedback pedal

ABSTRACT

A pedal has a control device ( 2 ) including a mobile pedal ( 6 ), elements for returning ( 20, 22 ) the control device returning the pedal ( 6 ) in its idle position as well as a force-feedback mechanism ( 4 ) to produce a hard spot when the pedal ( 6 ) is depressed. The force-feedback mechanism ( 4 ) includes an electric motor ( 28 ) designed to act on the control device ( 2 ), via one-way linking elements ( 36 ) and gear reduction elements, in the same direction as the return elements ( 20, 22 ). The one-way link prevents any action of the force-feedback mechanism ( 4 ) on the control device ( 3 ) in the direction opposite to the direction of action of the return elements ( 20, 22 ). The one-way link advantageously includes a clearance which enables the electric motor ( 28 ) to rotate in the direction allowing it to act on the control device ( 2 ) without acting immediately on the device.

The present invention relates to an immediate thrust return pedal.

A thrust return pedal is used in the field of driving assistance for amotor vehicle and therefore serves as an interface between the vehicleand its driver.

This type of pedal is for example used in the field of speed regulation.There are regulators which automatically manage the speed of thevehicle. It therefore suffices to select a cruising speed and anelectronic management system ensures that the vehicle is kept at thisspeed. Speed regulation can also be carried out by creating a hard pointduring the depression of the accelerator pedal. When the set speed isthen reached, the driver feels a hard point in this pedal and he thusknows that the set speed has been reached.

The thrust return pedal acts in this case like a luminous or audiblealarm which warns the driver. The driver is then free to take note ornot to take note of this alarm. This type of information means has theadvantage of being perceived only by the driver and not by the otherpassengers.

The document FR 2 685 667 discloses a thrust return pedal. In thedisclosed device, a servomotor controlled by an electronic unit acts onthe pedal by modifying a return force which depends on the intervalbetween the actual speed and the set limit speed value. The mechanismdescribed is such that when the set speed has been reached the mechanismcauses the pedal to gradually harden. The stiffness of the thrust returnmechanism varies progressively and it is found that the hard point takeseffect slowly. Because of this, the feeling created in the driver's footis not very pleasant.

The mechanism described in this document acts by only varying thestiffness of the pedal return mechanism. In particular, it does notallow instantaneous control of the thrust to be applied to the pedal nordoes it allow rapid vibrations to be produced in the pedal. Moreover, inthe event that the thrust return mechanism should malfunction, it mayarise that the return force with the maximum stiffness is then appliedcontinuously to the pedal. This does not affect the safety of thevehicle but it is uncomfortable.

Finally, the mechanism described has a relatively large overall sizesuch that it cannot be integrated into a pedal module as currentlyfitted to many motor vehicles.

It is thus an aim of the present invention to provide a thrust returnpedal in which the thrust applied to the pedal is immediate and wellcontrolled. Advantageously, the occurrence of a hard point will beimmediate when the conditions for establishing this hard point have beenproduced. Preferably, this pedal will additionally make it possible tovary the point of application of the hard point and also the amplitudeof this hard point. In one embodiment, it will be advantageous for analert message, in the form, for example, of a vibration of the pedal, tobe able to be transmitted to the driver.

To this end it proposes a thrust return pedal comprising a controldevice having a control member that moves between a raised position ofrest and a position of maximum depression, return means of the controldevice returning the control member to its position of rest, and athrust return mechanism designed to create a hard point during thedepression of the control member.

According to the invention, the thrust return mechanism comprises anelectric motor intended to act on the control device, by theintermediary of unidirectional connection means and possibly alsoreduction means, in the same direction as the return means of thecontrol device, the unidirectional connection prohibiting any action ofthe thrust return mechanism on the control device in the directionopposite to the direction of action of the return means.

In this new design, the electric motor does not just carry out anadjustment allowing the stiffness of a control member to be adjusted butalso exerts a force transmitted directly, or by the intermediary of areduction, to this control member. This allows better control of theaction applied to this control member. The thrust return pedal accordingto the invention thus makes it possible to have a hard point present ata predetermined (fixed or variable) position of the travel of thecontrol device and not a hard point which is established when thecontrol device reaches a predetermined position. With a device accordingto the invention, it is possible for each position of the control memberto be assigned a force, which is variable over time, to be applied tothis member to keep it in this position according to a predetermined lawthat can vary over time. The variation of this force to be applied isobtained by managing the value of the current feeding the electricmotor. In this way, the amplitude of the hard point may be adapted bythe motor which acts on the control device.

In a preferred embodiment, the unidirectional connection has aflexibility which makes it possible, according to the relative positionof the control device and of the thrust return mechanism, to depress thecontrol member as far as the hard point without transmitting thrust tothe thrust return mechanism. Because of this flexibility, the controldevice and the thrust return mechanism may work independently of oneanother as long as the connection is free, that is to say where nothrust is transmitted from the thrust return mechanism to the controldevice (or vice versa). By contrast, when the connection is blocked, theuser who depresses the control member does so against the force suppliedby the electric motor of the thrust return mechanism or else thismechanism acts to raise the control member.

To make it possible to have a hard point whose position is variableduring the depression of the control member, the electric motoradvantageously allows adjustment of the position of a connection memberand the unidirectional connection means are arranged between thisconnection member and the control device. In this embodiment, theconnection member is, for example, a spindle whose angular position isadjusted by the electric motor.

Several means of different type may be used to produce theunidirectional connection. A first embodiment of such a connectionemploys, for example, a free wheel which rotates freely in onedirection, without transmission of force, and in engagement in the otherdirection when a catch has been reached. Several other means may beemployed here. In a preferred embodiment, the unidirectional connectionis produced by a flexible link. This is, for example, a cable or a stripof flexible material.

A cable-type reduction is preferably provided between the electric motorand the connection member. In this way, when the unidirectionalconnection is engaged, the forces transmitted by a user on the controldevice are retransmitted to the motor with a lesser torque. Tests alsodemonstrated that this reduction made it possible to reduce the unwantedvariations in the torque of the electric motor which are transmitted tothe control member, this being more pleasant for the user.

In an embodiment which is well suited to a thrust return pedal accordingto the invention, the control device comprises a control pedal acting bythe intermediary of a connecting rod on a part which pivots about anaxis, the return means act on this pivoting part and this pivoting partis connected to the unidirectional connection means. In this case, theunidirectional connection means advantageously consist of a flexiblestrip of which one end is fixed tangentially to the pivoting part suchthat the strip winds flat around the pivoting part when the controlmember has been depressed. In this precise embodiment, when the electricmotor then acts on a connection member in the form of a spindle in orderto position it angularly this connection member is advantageouslymounted parallel with the pivoting part and faces it, the pivoting partpivots by less than 180° about its axis and the flexible strip isadvantageously fastened to the pivoting part in a peripheral zone of thepivoting part still situated facing away from the connection member.

The details and advantages of the present invention will become moreapparent from the following description, given with reference to theappended diagrammatic drawing in which:

FIG. 1 is a perspective view of a thrust return pedal according to theinvention,

FIG. 2 is a side view of the device shown in FIG. 1,

FIG. 3 is a cross-sectional view along the line III-III of FIG. 2,

FIG. 4 is a perspective view on a bigger scale of a detail of a cableand pulleys transmission system,

FIG. 5 is a response curve of a conventional pedal without thrustreturn, and

FIG. 6 is a response curve of the thrust return pedal shown in FIGS. 1to 3.

The thrust return pedal shown in the drawing comprises, on the one hand,an actuating mechanism 2, hereafter also referred to as a controldevice, and, on the other hand, a thrust return mechanism 4. These twomechanisms are connected by a unidirectional connection described belowand are both mounted on the same support.

The actuating mechanism 2 is a mechanism known to those skilled in theart. Such mechanisms are mounted in series on many motor vehicles.

The control device shown in the drawing comprises a control pedal 6mounted such that it pivots about a spindle 8. At its end opposite tothat of the spindle 8, the pedal is connected by the intermediary of aball joint to a connecting rod 10 in order to act on a ring 12 mountedsuch that it pivots about a fixed spindle 14. The connection between theconnecting rod 10 and the ring 12 is also made by means of a ball jointarticulated at the end of an arm 16 integral with the ring 12. By meansof this connection, when the control pedal 6 pivots about the spindle 8,it induces a rotation of the ring 12 about its fixed spindle 14. A Halleffect position sensor 18 is mounted on the fixed spindle 14 andmeasures the position of the ring 12 with respect to that fixed spindle14.

Two return springs 20 act on the ring 12 in order to bring the latterback to the position of rest, corresponding to the position assumed bythe actuating mechanism when no thrust is applied to the control pedal6. The return springs 20 act on the ring 12 by the intermediary ofcables 22 fixed to the ring 12 at one of their ends, each of the otherends being fixed to a return spring 20. Each return spring 20 isfurthermore attached to a fixed point of the support of the thrustreturn pedal. In the drawing, the return springs act on the ring 12 andtend to make the latter rotate in the clockwise direction (seen in thesame direction as in FIG. 2).

The position of rest of the control pedal 6 is defined (FIG. 2) by ahook 24 fixed under the control pedal 6 and cooperating with a fixedstop 26. As the connections between the ring 12 and the control pedal 6are ball joints, the forces applied by the cables 22 and the springs 20to the ring 12 are retransmitted to the control pedal 6 and vice-versa(apart from the slight friction losses of the ball joints).

The actuating mechanism such as described above corresponds to aconventional mechanism. The driver of the corresponding motor vehicleacts on the control pedal 6. In the rest of the description it isconsidered that this control pedal is an accelerator pedal. Depending onthe power that the engine must deliver, the driver depresses the controlpedal 6 to a greater or lesser degree. The position sensor 18 makes itpossible to know exactly the position of this control pedal 6 and itsdepression. This information is then supplied to an engine managementdevice and is used for regulating, for example, the angle of opening ofa fresh air inlet butterfly valve.

The thrust return mechanism 4 comprises an electric motor 28 used foradjusting the position of a pivoting spindle 30. The latter is parallelwith the fixed spindle 14. Each of these spindles 14, 30 carries apulley, 32 and 34 respectively, the two pulleys facing each other. Thepulley 32 mounted on the fixed spindle 14 is integral with the ring 12whilst the pulley 34 forms only a single part with the pivoting spindle30. The two pulleys 32 and 34 are connected to each other by a flexiblestrip 36 made, for example, from steel (foil) or from a compositematerial.

The strip 36 is fixed to the pulley 32 in such a way that, whatever thedirection of rotation of the pulley 34 may be, the strip 36 can act onthe ring 12 only in the direction of return of the control pedal 6towards its position of rest. In the embodiment shown in the drawing,the ring 12 and therefore also the associated pulley 32, have an angulartravel of the order of 60°, that is to say much less than 180°. In thiscase, there is a zone of the pulley 32 which never faces the pulley 34and is always facing away from it. The flexible strip 36 thereforebecomes fixed on such a zone tangentially to the pulley 32. When thering 12 pivots following a depression of the control pedal 6, theflexible strip 36 winds flatly over a part of the periphery of thepulley 32, without forming folds. This flexible strip 36 is fixed in asimilar way to the pulley 34. However, as the amplitude of the movementof this pulley 34 can be greater than 180°, the attachment zone of theflexible strip 36 is not necessarily facing away from the pulley 32. Thethrust return pedal management device will ensure that the motor 28drives the movement of the pulley 34 in such a way that the flexiblestrip 36 winds around the pulley 34 without forming folds.

The motor 28 acts on the pivoting spindle 30 by the intermediary of areduction unit. For reasons of size, the axis of the motor 28 is notmounted parallel with but perpendicular to the axis of the pivotingspindle 30. Two stages of reduction are provided between the motor 28and the pivoting spindle 30.

The electric motor 28 comprises an output shaft 38 integral with apulley 40 of small diameter. A metal cable connects this pulley 40 to apulley of large diameter 42. The latter is mounted such that it pivotson an intermediate spindle 44, parallel with the pivoting spindle 30 andthe fixed spindle 14. Return pulleys 46 are provided for the cable 48connecting the pulleys 40 and 42.

The intermediate spindle 44 also carries a pulley 50 of small diametercooperating, by the intermediary of a cable 52, with a pulley of largediameter 54. This latter pulley is integral with the pivoting spindle30. Each cable 48, 52 corresponds to a reduction stage. Such a stage isshown in FIG. 4. It is the stage that makes use of the cable 52.

The pulley 54 consists of two half-pulleys 54 a and 54 b. These twohalf-pulleys are of identical diameter and are mounted coaxially on thepivoting spindle 30. A spring 56 acting torsionally connects the twohalf-pulleys 54 a and 54 b.

Each end of the cable 52 is provided with a stop ball 58 and eachhalf-pulley 54 a and 54 b is equipped with a corresponding recess 60intended to receive a stop ball 58. Thus, one end of the cable 52 isfixed to the half-pulley 54 a by the intermediary of a stop ball 58 andthe corresponding recess 60. The cable then winds over a part of theperiphery of that half-pulley 54 a and is then wound by several turnsaround the pulley of small diameter 50 and is finally wound around apart of the periphery of the second half-pulley 54 b, the other end ofthe cable 52 being fixed to this half-pulley 54 b by the intermediary ofthe second stop ball 58 and of the corresponding recess 60. Because ofthe spring 56 and the degree of freedom of rotation between the twohalf-pulleys 54 a and 54 b, the cable 52 is always tensioned.

It will be noted on FIG. 4 that the cable 52 comprises a third stop ball62. The latter is placed for example at mid-length on the cable 52. Ittakes its place in a corresponding recess 64 formed in the pulley 50. Inthis way, no slipping can impede the transmission of the movement of themotor 28 from the pulley 50 to the pulley 54 or, more precisely, thehalf-pulley 54 a.

The transmission between the pulley 40 and the pulley 42 is carried outin the same way. As already mentioned above, in this transmission thereare return pulleys 46 which, apart from the change of orientation, donot change the kinematics of the mechanism in any way. Another minordifference is that the cable 48 is not provided with a stop ball at itscenter. Such a ball and a corresponding recess could of course beprovided but they are optional considering the slight forces applied tothe cable 48 and therefore the very low risk of slipping of this cablearound the pulley 40.

The position of the pivoting spindle 30 is measured by means of apotentiometer 66. The information provided by this potentiometer 66makes it possible to know exactly the angular position of the pivotingspindle 30 and therefore of the pulley 34 also. This information,combined with that given by the Hall effect sensor 18, makes it possibleto know the play present in the flexible strip 36.

The functioning of the thrust return pedal described above withreference to FIGS. 1 to 4 is therefore as follows.

This thrust return pedal can firstly function like a conventional pedal.It is assumed here that it is an accelerator pedal. It thereforesuffices to position the pivoting spindle 30 in a position such that,whatever the position of the ring 12 and therefore of the pulley 32 maybe, the flexible strip 36 is never tensioned. It therefore suffices toprovide a flexible strip 36 of sufficient length. This length iscalculated according to the distance separating the fixed spindle 14 andthe pivoting spindle 30, the diameters of the pulleys 32 and 34 and alsothe positions of attachment of the flexible strip 36 on these pulleys.

The behavior of the control pedal 6, not equipped with a thrust returnmechanism, is represented diagrammatically in FIG. 5. In this figure,the angle of depression A of the pedal which corresponds to the positionof the control pedal 6 with respect to its spindle 8, a positiondirectly proportional to the angle of rotation of the ring 12, isplotted along the horizontal axis. The force F applied by a driver'sfoot on the control pedal 6 is plotted along the vertical axis. In thecurve seen in this FIG. 5 it appears that the force to be applied inorder to actuate the control pedal 6 must initially (see reference 80)overcome the return force of the springs 20, intended to return saidpedal to its position of rest, and then the law follows a linear form(see reference 82). When the control pedal 6 is released, the return tothe position of rest also follows a linear law (see reference 84). Thecurve seen in FIG. 5 shows a hysteresis of the control pedal 6 due, inparticular, to the friction produced between the cables 22 and the ring12. This behavior is sought in order to increase the comfort andergonomics of this control pedal 6.

When it is desired that the driver should feel a hard point during thedepression of the pedal, the electric motor 28 is operated and theflexible strip 36 is tensioned in such a way that when the control pedal6 arrives at the position where the hard point must appear, the flexiblestrip 36 is then tensioned. When the control pedal 6 therefore arrivesin the position where the flexible strip 36 is just tensioned, in orderto continue to depress the control pedal 6 it is necessary, on the onehand, to continue to overcome the return force of the springs 20 and, onthe other hand, to cause the pivoting spindle 30 to pivot against theforce applied to this spindle by the motor 28, which acts by theintermediary of the reduction means described above.

A diagrammatic representation of behavior can again be seen in FIG. 6.In this figure, the behavior of a conventional pedal without thrustreturn such as shown in FIG. 5 has been plotted as a reminder. The newcurve reveals the presence of a hard point for an angle of depression αof the control pedal 6. This hard point is represented on the curve byquasi-vertical portions 86 of the curve.

Beyond the hard point, the behavioral law follows a conventional linearform with the presence of hysteresis (see reference 88).

It is noted that the hard point appears without transition. Thestiffness felt by the driver varies suddenly. In fact, in this case thethrust return mechanism works independently of the actuating mechanism.If the instruction given is to form a hard point when the angle ofdepression of the control pedal 6 is equal to α, the electric motor 28acts consequently in order to position the pivoting spindle 30correctly. This adjustment is carried out as soon as the instructionvalue is known and it is carried out before the control pedal 6 reachesthe corresponding position. The thrust return is therefore present whenthe control pedal 6 reaches the specified position and is notestablished solely when the control pedal reaches this position.

Once the flexible strip 36 is tensioned, by varying the value of thecurrent feeding the electric motor 28, it is possible to vary theamplitude of the hard point. These different amplitudes are representeddiagrammatically in FIG. 6 by dotted lines (depression of the pedal 6)and by dotted and dashed lines (release of the pedal 6). It is thuspossible to create a hard point that can be overcome easily or a hardpoint that is difficult to overcome by the driver. This makes itpossible to provide the driver with different kinds of information.

The thrust return mechanism according to the invention also makes itpossible to make the driver feel vibrations in his foot, via the controlpedal 6. In order to do this it suffices to supply the electric motor 28with current in an alternating manner. An additional means is thusavailable for providing the driver with information.

In an extreme case, it is even possible to imagine that the motorapplies to the pivoting spindle 30, and therefore to the flexible strip36 and the ring 12, sufficient force to bring the control pedal 6 backto its position of rest. This can for example be envisaged incooperation with a safety device, for example detecting the driverfalling asleep or other parameters.

It is noted that if, for one reason or another, the thrust returnmechanism should fail, it would not in any case cause the control pedal6 to be locked and it always allows the latter to be returned to itsposition of rest.

For the exceptional case in which a large force would be applied to thecontrol pedal 6 whilst the flexible strip 36 is tensioned, in order notto transmit this large force to the electric motor 28 and to protect thelatter, a declutching device 68 is provided between the pivoting spindle30 and the electric motor 28. This declutching device 68 is for exampledisposed between the pivoting spindle 30 and the pulley 54. It is thusguaranteed that no torque greater than a predetermined torque can betransmitted to the electric motor 28.

In the thrust return pedal described above, the electric motor actsdirectly on the control pedal 6. Because of the original transmission bycables and pulleys used here, the electric motor supplies minimum force(reduced friction) and can be chosen from a range of small-sized motorswhose cost is advantageously relatively low. Another transmission mode,for example by gears, would necessitate a more voluminous and morecostly motor. The reduction is of course chosen such that the pressingforce of the driver's foot on the control pedal 6, even when the driverdecides to disregard the warning given by the thrust return mechanism,will not generate excess current in the motor and thus will not riskdamaging it.

The unidirectional connection, achieved here by the flexible strip 36,between the thrust return mechanism and the control pedal actuatingmechanism, allows the return springs 20 to act freely on the controlpedal, independently of the thrust return mechanism. This guarantees,firstly, that only the depression of the control pedal beyond the hardpoint is mechanically braked, whereas the return to the position of restis free of any braking, the flexible strip not opposing the working ofthe return springs. This total decoupling between the thrust returnmechanism and the control pedal actuating mechanism allows greatflexibility in the (electronic) management of the thrust return pedalaccording to the invention.

The thrust return pedal such as described above can be embodied in theform of a module that is simply screwed and connected at the placeallocated for the accelerator pedal in a motor vehicle. This device canbe sufficiently compact so as not to obstruct the adjacent brake controlpedal.

This pedal also has the advantage that one and the same device makes itpossible to have very variable behavioral laws: position of the hardpoint over the whole range of depression of the control pedal, amplitudeof the hard point, sending of vibration to the control pedal, etc.

The present invention is not limited to the embodiment described aboveby way of non-limiting example. It also relates to all of the variantembodiments within the capabilities of those skilled in the art coveredby the following claims.

Thus, the invention has a main application related to the acceleratorpedals of motor vehicles. However, other applications can be envisaged:control lever for any type of machine, industrial or domestic, gamejoystick, etc.

The number of reduction stages is two in the example described above. Asingle stage or, on the contrary, several stages, can also be envisaged.

The flexible strip producing a unidirectional connection between thepedal actuating mechanism and the thrust return mechanism could bereplaced for example by a free wheel.

The tension of the slack length in each reduction stage could beachieved in a different manner than by using, as described above, splitpulleys incorporating a tension spring.

1. A thrust return pedal comprising a control device (2) having acontrol member (6) that moves between a raised position of rest and aposition of maximum depression, return means (20, 22) of the controldevice returning the control member (6) to its position of rest, and athrust return mechanism (4) designed to create a hard point during thedepression of the control member (6), characterized in that the thrustreturn mechanism (4) comprises an electric motor (28) intended to act onthe control device (2), by the intermediary of unidirectional connectionmeans (36) and possibly also reduction means, in the same direction asthe return means (20, 22) of the control device (2), the unidirectionalconnection prohibiting any action of the thrust return mechanism (4) onthe control device (2) in the direction opposite to the direction ofaction of the return means (20, 22).
 2. The thrust return pedal asclaimed in claim 1, characterized in that the unidirectional connectionhas a flexibility which makes it possible, according to the relativeposition of the control device (2) and of the thrust return mechanism(4), to depress the control member (6) as far as the hard point withouttransmitting thrust to the thrust return mechanism (4).
 3. The thrustreturn pedal as claimed in claim 1, characterized in that the electricmotor (28) allows the position of a connection member (34) to beadjusted and in that the unidirectional connection means (36) arearranged between this connection member (34) and the control device (2).4. The thrust return pedal as claimed in claim 3, characterized in thatthe connection member (34) is a spindle whose angular position isadjusted by the electric motor (28).
 5. The thrust return pedal asclaimed in claim 1, characterized in that the unidirectional connectionis produced by a flexible link (36).
 6. The thrust return pedal asclaimed in claim 1, characterized in that a reduction is providedbetween the electric motor (28) and the connection member (34).
 7. Thethrust return pedal as claimed in claim 4, characterized in that thecontrol device (2) comprises a control pedal (6) acting by theintermediary of a connecting rod (10) on a part (12) that pivots aboutan axis, in that the return means (20, 22) act on this pivoting part(12) and in that this pivoting part (12) is connected to theunidirectional connection means (36).
 8. The thrust return pedal asclaimed in claim 7, characterized in that the unidirectional connectionmeans consist of a flexible strip (36) of which one end is fixedtangentially to the pivoting part (12) such that the strip (36) windsflat around the pivoting part (12) when the control member (6) isdepressed.
 9. The thrust return pedal as claimed in claim 8,characterized in that the connection member (34) is mounted parallelwith the pivoting part (12, 32) and faces it, in that the pivoting part(12, 32) pivots by less than 180° about its axis and in that theflexible strip (36) is fastened to the pivoting part (12, 32) in aperipheral zone of the pivoting part still situated facing away from theconnection member (34).
 10. The thrust return pedal as claimed in claim2, characterized in that the electric motor (28) allows the position ofa connection member (34) to be adjusted and in that the unidirectionalconnection means (36) are arranged between this connection member (34)and the control device (2).
 11. The thrust return pedal as claimed inclaim 1, characterized in that the control device (2) comprises acontrol pedal (6) acting by the intermediary of a connecting rod (10) ona part (12) that pivots about an axis, in that the return means (20, 22)act on this pivoting part (12) and in that this pivoting part (12) isconnected to the unidirectional connection means (36).